Ancient Hominins and Early Humans May Have Engaging in Intimate Contact, Researchers Propose

Among Galápagos albatrosses to Arctic mammals, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Now, scientists suggest that ancient hominins also engaged in this behavior – and might even have exchanged kisses with modern humans.

Shared Oral Evidence

It is not the first time experts have suggested ancient relatives and early modern humans were closely connected. Among previous studies, scientists have discovered modern people and their thick-browed cousins possessed the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, implying they exchanged oral fluids.

"Probably they were engaging in intimate contact," the researcher noted, explaining that the idea aligned with research that has found humans of certain genetic backgrounds have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.

Romantic Interpretation

"This offers a more romantic perspective on ancient interactions," Brindle said.

Writing in the publication a scientific periodical, Brindle and colleagues detail how, to investigate the historical roots of intimate contact, they first had to come up with a description that was not restricted by how people kiss.

Defining Kissing

"Previously there were some efforts to describe a intimate act, but it's largely human-centric, which means that basically other animals do not engage in this. Now we understand that they probably do, it may appear different from what our intimate contact looks like," said the evolutionary biologist.

Nonetheless, she noted some actions that looked like kissing were distinct activities – such as the processing and transfer of food, or "kiss-fighting", observed in aquatic species known as French grunts.

Consequently the research group developed a definition of intimate contact centered around friendly interactions involving directed mouth-to-mouth contact with a member of the same species, with some movement of the mouth but absence of food.

Research Approach

Brindle said they focused on accounts of intimate behavior in primates from Africa and Asian regions, including primates, chimpanzees and orangutans, and used digital recordings to verify the reports.

The researchers then combined this information with information on the genetic connections between extant and ancient types of such animals.

Historical Timeline

The team propose the results indicate kissing evolved approximately 21.5m and 16.9 million years ago in the predecessors of the great primates.

The position of Neanderthals on this family tree means it is probable they, too, indulged in a kiss, the scientists conclude. But the activity might not have been limited to their specific group.

"Reality that humans kiss, the reality that we now have shown that ancient relatives very likely engaged, suggests that the two [species] are probably did engage," the researcher noted.

Evolutionary Importance

While the scientific reasoning is discussed, the expert said kissing could be employed in reproductive situations to possibly enhance reproductive success or assist in selecting between partners, while it could assist strengthen connections when practiced in a platonic way.

A separate researcher in the activities of great apes commented that as intimate contact was observed in a wide range of apes it was logical its origins lie deep in our ancient history, and an analysis of various types of intimate behavior among a wider variety of animals might push its beginnings back further still.

"Things that we consider as characteristics of human life, like kissing, are not exclusive to us if we examine carefully at different species," he said.

Social Elements

An archaeology expert said that kissing had a social component as it was not common to all human groups.

"However, as humans we succeed or struggle on the quality of our relationships, and methods of promoting trust and closeness will have been significant for eons," she said. "It might be an image that appears a bit incongruous to our incorrect assumptions of a supposedly aggressive and aggressive past, but actually it ought to be expected that ancient hominins – and even them and our own species together – kissed."